ISLAM UNDER FIRST FOUR CALIPHS 31 entire success, had been Caliph for ten years and, although sixty years old, was still full of energy when an assassin's knife laid him low. A Persian slave, known as Abu Lulu, complained to the Caliph that he was assessed too heavily by his master at two dirhems a day. Omar, who knew the man, replied that for a clever artificer like him, who was believed to be able to construct a mill driven by wind,1 the amount was not excessive. Abu Lulu made a threatening reply, and the following morning stabbed the Caliph while he was leading the prayers in the mosque. Thus died the greatest Moslem after the founder of the religion himself, a man of courage, simplicity, sagacity, and a passion for justice and duty,2 a combination of qualities which eminently fitted him to control the destinies of Islam during the critical decade of conquest. Nevertheless in Persia the name of Omar is execrated, and the anniversary of his death is celebrated as a day of rejoicing by Persians. Until recently they were accus- tomed to burn the effigy of the Caliph who conquered Iran. The Accession of Othman, A.H. 24 (644).—Omar upon his death-bed expressed the wish that Abd-al-Rahman should be his successor, but he refused, and the matter was referred to a body of electors. In the end, how- ever, Abd-al-Rahman was permitted to make the choice. For long he wavered between AH and Othman, but! finally declared the latter to be the Caliph. Othman'si reign lasted for twelve years, but from the outset it was clear that he did not possess the necessary qualities for dealing effectively with a difficult situation. Even under the iron rule of Omar it was impossible to curb the insubordinate spirit shown by the Arabs of Kufa and Basra. The best hope lay in maintaining the prestige of the Kureish tribe, but this powerful instrument was weakened through the impolicy of Othman, who favoured his own branch, the Omayyad, with the result that the influence of the Kureish was paralysed by divisions which were widened by lapse of time, ^ 1 This is believed to be the earliest mention of a windmill. Vide also Chapter I» 1? 2 It was a favourite maxim of Omar's that " the most miserable Governor is he * whose subjects are miserable."